Backgrounds & Objects: The aim of this study was to investigate the radioprotective effect of Shengmai-san(SMS), a herbal medicine, on mice jejunal crypt cell survival and Apoptosis. Methods: Mice were devided into 4 groups according to radiation dose and SMS treatment: Normal was the group without irradiation. Control was the group treated with D.W before 10 Gy irradiation. SMS 2.9 was sample group treated with 2.9 mg/10 g of SMS extract before 10 Gy irradiation and SMS 29 was sample group treated with 29 mg/10 g of SMS extract before 10 Gy irradiation. And Each group were sacrificedat 24 hours and 72 hours after irradiation. To analyze the crypt survival, hematoxylin-eosin staining was used and to analyze the apoptosis, the TUNEL assay was done. Results: 1. From the microcolony survival assay, the SMS 2.9 and SMS 29 showed the radioprotective effect with a statistical significance compared to the control group at 24 hr (P < 0.01) and 72 hr (p < 0.001) after 10 Gy irradiatien. And the differences of radioprotective effect between SMS 2.9 and SMS 29 were net significant. 2. The results of the TUNEL assay showed that the apoptotic index in SMS 2.9 and SMS 29 was significantly decreased, as compared to the control group at both 24 hr ( p < 0.01) and 72 hr (SMS 2.9 : p < 0.001. SMS 29 : P < 0.01) after 10Gy irradiation And the differences of between SMS 2.9 and SMS 29 were not significant. Conclusions: It could be suggested that the Shengmai-san has a prominent Protective effect in mice intestines against the radiation damage. And the radieprotective effect seems to be related to inhibition of the apoptosis.